diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index b807275ea73936377921481107f765acb866d589..a34e86630f2637728f6e25ebaebe174e3cd03738 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3446,6 +3446,7 @@
 
 #define GEN6_UCGCTL2				0x9404
 # define GEN6_RCPBUNIT_CLOCK_GATE_DISABLE		(1 << 12)
+# define GEN6_RCCUNIT_CLOCK_GATE_DISABLE		(1 << 11)
 
 #define GEN6_RPNSWREQ				0xA008
 #define   GEN6_TURBO_DISABLE			(1<<31)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 2b2a7645cd0c47aea8319e3e1e2f73f26d10b27f..591eb0ed311036a313f15527cf834555d6eae2b0 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8154,8 +8154,13 @@ static void gen6_init_clock_gating(struct drm_device *dev)
 	 * some amount of runtime in the Mesa "fire" demo, and Unigine
 	 * Sanctuary and Tropics, and apparently anything else with
 	 * alpha test or pixel discard.
+	 *
+	 * According to the spec, bit 11 (RCCUNIT) must also be set,
+	 * but we didn't debug actual testcases to find it out.
 	 */
-	I915_WRITE(GEN6_UCGCTL2, GEN6_RCPBUNIT_CLOCK_GATE_DISABLE);
+	I915_WRITE(GEN6_UCGCTL2,
+		   GEN6_RCPBUNIT_CLOCK_GATE_DISABLE |
+		   GEN6_RCCUNIT_CLOCK_GATE_DISABLE);
 
 	/*
 	 * According to the spec the following bits should be